Various investigations have been made for many years on silver halide photographic materials to obtain a high image density (D.sub.max) and a high sensitivity in spite of using a small amount of silver. In particular, the need for rapid processing of silver halide photographic materials has recently increased. Therefore, it is an important subject to reduce the amount of silver, more specifically to obtain an emulsion of high sensitivity containing fine grains from the standpoint of shortening a time for fixing, washing with water and drying.
On the other hand, in the field of photo-mechanical processes, there are demands for photographic light-sensitive materials having satisfactory image reproducibility, stability of processing solutions, and simplification of replenishment in order to handle the recent diversity and complexity of printed materials.
In particular, originals in line work are comprised of photo-composed letters, hand-written letters, illustrations, dot prints, etc. and thus contain images having different densities or line widths. It has been keenly demanded to develop a process camera, a photographic light-sensitive material or an image formation system which enables good reproducibility of the original. In the photomechanical process for catalogues or large posters, on the other hand, enlargement or reduction of a dot print is widely conducted. When a dot print is enlarged in plate making, the line number becomes small and the dots are blurred. When a dot print is reduced, the line number/inch becomes larger and the dots become finer than the original. Accordingly, an image formation system having a broader latitude has been demanded for maintaining reproducibility of halftone gradation.
A halogen lamp or a xenon lamp is employed as a light source of a process camera. In order to obtain photographic sensitivity to these light sources, photographic materials are usually subjected to orthochromatic sensitization. However, such orthochromatic materials are more susceptible to influences of chromatic aberration of a lens and thus liable to image quality deterioration. The deterioration is conspicuous when using a xenon lamp as a light source.
Known systems meeting the demand for broad latitude include a method comprising processing a lithographic silver halide light-sensitive material comprising silver chlorobromide (containing at least 50% of silver chloride) with a hydroquinone developer having an extremely low effective sulfite ion concentration (usually 0.1 mol/l or less) to thereby obtain a line or dot image having high contrast and high density in which image areas and non-image areas are clearly distinguished as described, for example, in The Journal of Photographic Science, 293, Vol. 22 (1974), A Review of the Chemistry of Lith (Infections) Development (by M. Austin). According to this method, however, development is extremely unstable against air oxidation due to the low sulfite concentration of the developer. Hence, various efforts and devices are required to stabilize the developing activity and, also, the processing speed is quite low, to reduce working efficiency.
An image formation system is desired which eliminates the image formation instability associated with the above-described lith development system and provides a ultrahigh contrast image by using a processing solution having satisfactory preservation stability. In this connection, it has been proposed to develop a surface latent image type silver halide photographic material containing a specific acylhydrazine compound with a developing solution having a pH between 11.0 and 12.3 and containing at least 0.15 mol/l of a sulfite preservative and thereby exhibiting satisfactory preservation stability to form a ultrahigh contrast negative image having a gamma exceeding 10, as disclosed in U.S. Pat. Nos. 4,166,742, 4,168,977, 4,221,857, 4,224,401, 4,243,739, 4,272,606, and 4,311,781. In this new image formation system, silver iodobromide and silver chloroiodobromide as well as silver chlorobromide can be used, while the conventional ultrahigh contrast image formation systems are only applicable to photographic materials comprising silver chlorobromide of high silver chloride content.
While the above-described image formation system exhibits excellent performance in dot quality, stability of processing, rapidness of processing, and reproducibility of originals, a system in which reproducibility of originals is further improved is desired to handle the recent diversity of printed materials.
In systems using hydrazines, silver iodide is introduced into silver halide grains for various purposes as described in JP-A-61-29837, JP-A-62-55643 and JP-A-64-61744 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") as well as the above mentioned patents.
Silver halide emulsions containing silver halide grains obtained by epitaxial growth of silver halide which has a halide composition different from that of host grains are described in U.S. Pat. Nos. 4,142,900, 4,463,087 and 4,471,050, JP-A-59-119344, JP-A-59-119350, JP-A-55-163532, JP-A-56-27134, JP-A-55-161229, JP-A-58-108526 and JP-A-62-7040. Further, conversion of corner sites of cubic silver halide grains having a silver chloride content of not less than 90 mol % with silver bromide is described in Japanese Patent Application No. 62-324567 (corresponding to JP-A-1-166039).
Incorporation of redox compound capable of releasing a development inhibitor upon being oxidized into systems using hydrazines is described in JP-A-61-213847 and JP-A-64-72140.